LEDs for Pico Projectors BA SID Chapter/PDF and Images... · Hong Kong - Headquarter Asia - Sales Asia Pacific - Marketing Asia Pacific Yokohama - Sales Japan - Marketing Japan -

LEDs for Pico

Projectors

BA SID

18 April 2012

LED for Pico Projectors| Page 2

18 April 2012 | FN

Agenda

Introduction

LED requirements

Architecture of Projector Engine

Etendue

Chip Technologies

Light Extraction

Design Rules for LED

Optical Architecture

Converted Green

LED Drive Electronics

New Chip architecture

Summary


18 April 2012 | FN

Regensburg, Germany

- Global Headquarter-Shanghai

- Sales China- Marketing China

- Application Center

Hong Kong

- Headquarter Asia- Sales Asia Pacific

- Marketing Asia Pacific

Yokohama

- Sales Japan- Marketing Japan

- Application Center

Penang

- Backend Plant- Frontend Plant

- R&D Asia

Northville

- Sales & Marketing NA East- Application Center

OSRAM Opto Semiconductors - company overview

Sunnyvale, CA

- Headquarters NA

- Sales and Service NA West


18 April 2012 | FN

Package Design

power package

micro package

SMT-TOPLED®

EPI

InGaAlP thin film InGaAlP high optical

power

Chip Designsingle chip device

Conversion

350 400 450 500 550 600 650 nm

chip phosphor package

emission spectrum

+ +

OSRAM – Vertically Integrated * *


18 April 2012 | FN

Definition of a Pico-Projector *

Definition offered by Dr. William Coggshall, president of Pacific Media Associates


18 April 2012 | FN

LED - Early Customer Requirements **

• High Luminance

• High efficiency

• Good thermal

performance

• Accurate chip

placement

•Auto alignment of

optics

• Thermal sensor

• Easy connection

• Compact sizeTooling Holes for

Optics Alignment


18 April 2012 | FN

Projection System – Lamp to LED **

Color wheel is eliminated in LED based system.

Frame Period

LED on/offR

G

B

Frame Period

LED on/offR

G

B


18 April 2012 | FN

Schematic of DMD based Sequential Color

Projector Engine

R

DMD

(Digital Micromirror Device)

DLP® (TI)

TIR prism

Projection lens

system

Homogenizing optics (Fly’s

Eye Array)

Collection/Collimating

lenses

Red LED

Dichroic

filters/mirrors

Relay optics

to screen

G

Green LED

B

Blue LED

Mirror


18 April 2012 | FN

Schematic of a LCoS based Projector Engine

D. Darmon, J. R. McNeil, M. A. Handschy,

“LED-illuminated Pico Projector

Architectures”,

SID 08 Digest, 170-173 (2008)


18 April 2012 | FN

Etendue = area of the source times the solid angle of the

system's entrance pupil subtends as seen from the source

)(sin22

LEDLEDLED AnE

φLED

Microdisplay

LED

Light

Source

ALED

φsystem

Ap

)(sin2

systempsystem AE

systemLED EE

Due to etendue considerations there is a maximum usable light emitting area, defined by

• Microdisplay size

• Microdisplay acceptance angle and projection lens F/#

• LED light collection angle by secondary optics (collection lens)

http://en.wikipedia.org/wiki/Solid_angle

http://en.wikipedia.org/wiki/Entrance_pupil

http://en.wikipedia.org/wiki/Subtend

http://www.lupenshop.de/


18 April 2012 | FN

Chip Technologies


18 April 2012 | FN

Thin-Film LED

Active layer

Reflective surface

carrier

5-10 µm

150 - 250 µm

The reflective surface of the carrier eliminates substrate absorption

Thin Film LEDs – 1st release 2004 **

Starting

substrate

carrier

epi

Starting

substrate

Sacrificial layercarrier


18 April 2012 | FN

Features of ThinFilm (also ThinGaN) LEDs **

Higher efficiency compared to

volume emitter (extraction efficiency

increased from 50% to 97%).

Lower Vf

Top emission only

minimizes etendue (good for

coupling to optics and light guides.

Improved color shift over angle.

Scalable of output to chip area.

Volume Emitter

Thin Film


18 April 2012 | FN

Light Extraction From A LED **

Flux = 100 lm

Luminance = 100 nits

Flux = 100 lm

Luminance = 100 nits

Take 2 identical chips of 1mm2 chip size


18 April 2012 | FN

Design Rule #1 – *Chip on Air* **

Flux = 93 lm

Luminance = 93 nits

Etendue = 1

Flux = 150 lm

Luminance = 67 nits

Etendue = 2.25

Add cover glass with

AR (anti-reflective) coating

Add dome lens optimized

for extraction with ñ = 1.5

=> Design rule #1: Use “chip on air” i.e. no silicon encapsulation


18 April 2012 | FN

Design Rule #2 – Use Largest Chip Size possible **

0%

20%

40%

60%

80%

100%

120%

1mm (40mil) 750µm (30mil) 500µm (20mil)

chip size

no

rma

lize

d lu

me

n o

utp

ut

@ 3

50

mA

ThinFilm

ThinGaN

0%

25%

50%

75%

100%

125%

150%

0 15 30 45 60 75 90 105 120 135 150

current density, A/cm2

rela

tive

lu

min

ou

s e

ffic

acy

ThinFilm

ThinGaN

Chip efficacy (lm/W) is reduced with increasing current density („current droop‟)

Red: ThinFilm based on AlInGaP material system

Green, Blue: ThinGaN based on InGaN material system

Relative luminous efficacy is normalized to 100% @ 350mA/mm² corresponding to 350mA for 1mm (40mil) chip.

=> Design rule #2: Maximize chip size


18 April 2012 | FN

Design Rule # 3 – Don„t Exceed System Etendue

)(sin

)(sin

)(sin)(sin

22

2

222

LED

systemp

LED

systempLEDLED

systemLED

n

AA

AAn

EE

=> Design rule #3:

Keep the chip size (emitting area) below the maximum limit defined by the optical

systems Etendue.

Best efficacy is reached if etendue of LED equals that of the optical system.

Maximum LED size based on system Etendue

Only for a LED smaller than this max size all light can be guided through the optics system.

For a LED larger than this max size part of the light is wasted.


18 April 2012 | FN

Optimum LED Solution: Examples

0.22 nHD, DMD 0.3 WVGA, DMD 0.21 WVGA, LCoS 0.28 720p, LCoS

Resolution 640 x 360 854 x 480 854 x 480 1280 x 720

Diagonal 0.22” 0.30” 0.21” 0.28”

Aspect ratio 16:9 16:9 16:9 16:9

F-Number 2.4 2.4 1.8 1.8

Acceptance angle 12 deg 12 deg 16 deg 16 deg

Etendue 1.74 mm²sr 3.24 mm²sr 2.74 mm²sr 4,86 mm²sr

LED collection

angle

+/-65 deg +/-65 deg +/-65 deg +/-65 deg

Optimum Chip size

(emitting area)

1.10mm x 0.62mm 1.50mm x 0.84mm 1.37mm x 0.77mm 1.83mm x 1.03mm

Optimum LED for 3-channel illumination using various micro displays


18 April 2012 | FN

0.65“ – 0.95“

Imager

high

low

OSTAR Projection

6x 1mm²

R,G,B,RB,RGB,UW

Metal Board VersionSMT Version

high

low

mid

Brightness

OSTAR Compact

3x 750um 1x 2mm²

RGB R,G,B,UW

2x 750um 1x 1mm²

RB, GB R,G,B

1x 750um CG

R,G,B

CG

0.55“ – 0.65“

OSTAR Power Projection

6x 2mm²

R,G,B

CG

OSTAR SMT

4x 1mm²

R,G,B,RGB,UW

4x 0.75mm

RGB

4x 0.5mm

RGB

2x 2mm²

R,G,B + CG

Product Portfolio for Projection

Converted Green

derivates

successful launched in time


18 April 2012 | FN

3-channel 2-channel

Optical Architecture: Overview

1-channel

3 discrete LED devices

Pros:

-Maximum etendue/lumens per color

-Good color uniformity

Cons:

-Large engine size

-High BOM

-Many components needed

2 discrete LED devices

Pros:

-Reduced engine size

-Reduced BOM

-Only 1 dichroic filter element needed

Cons:

-Colors in 2in1 pkg have limited

etendue

-Color homogenization needed

1 LED device only

Pros:

-Reduced engine form factor

-Reduced BOM

-No dichroic filters needed

Cons:

-Low etendue/lumens for each color

-Color homogenization needed


18 April 2012 | FN

3-Channel Illumination

Emitting area of optimum and standard LED chips for various imager panels

4x 500µm

750µm

1mm

2x 750µm

2mm²

4x 750mm

0

0.25

0.5

0.75

1

1.25

1.5

0 0.25 0.5 0.75 1 1.25 1.5 1.75 2

LED emitting length, mm

LE

D e

mittin

g w

idth

, m

m

0.22 nHD

DMD

0.3 WVGA

DMD

0.21 WVGA

LCoS

0.28 720p

LCoS


18 April 2012 | FN

System Settings

2-Channel Illumination with 0.30” WVGA DMD

1x 1mm

2x 750µm

Microdisplay panel: 0.30” WVGA DMD

Illumination architecture 2-channel G + RB

LEDs G 1mm + RB 2x 750µm

Frame rate 120Hz

Color overlap no color overlap

Target whitepoint on screen

Cx/Cy

0.29/0.33

Total optical efficiency 23% (G), 25% (RB)

Solderpoint temperature Ts 60°C

Schematic


18 April 2012 | FN

“Green Gap”

0%

25%

50%

75%

100%

350 400 450 500 550 600 650 700

wavelength (nm)

inte

rna

l e

ffic

ien

cy

InGaN

InGaAlP


18 April 2012 | FN

Green is generally Limiting Color in a Display. **

Brightness (Luminous Flux)

0

200

400

600

800

1000

1200

1400

0 1 2 3 4 5 6 7

Forward Current, A

Lu

min

ou

s F

lux

, lm

NEW Converted Green

Standard ThinGaN True Green

20ms single pulse

Spectral Curve @ 1.4A

0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1

350 450 550 650 750Wavelength, nm

Inte

nsit

y, n

orm

alized

to

max=

1

NEW Converted Green

Standard ThinGaN True Green

20ms single pulse

Ceramic Based Converted Green for Higher Lumens


18 April 2012 | FN

Spectral Curves – RGB vs Converted Green

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

300 350 400 450 500 550 600 650 700 750 800

wavelength, nm

op

tic

al

inte

ns

ity

, n

orm

ali

ze

d t

o m

ax

=1

Amber

True Green

Blue

V-lambda

Converted Green


18 April 2012 | FN

Usability of the Light by cutting Blue and Red **

Content of luminous flux within WL-range:

90% in 500…600nm

81% in 510…590nm

Blue and Red are cut by typical

multi-channel light engines

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

300 400 500 600 700 800Wavelength, nm

Inte

nsit

y, n

orm

alized

to

max=

1


18 April 2012 | FN

LED Drive Electronics **

Ideal Solution:

• Single chip solution with multi-channel control.

• Serial interface for drive control

• Onboard non-volatile memory to store calibration

data

• Accommodate Vf differences of AlInGaP vs. InGaN

• Permit color overlapping.


18 April 2012 | FN

Top view

New Chip Architecture: UX3 **

Conductive carrier

n

p

Cross sectional view

Conductive carrier

n

p

Cross sectional view

Luminance @ 1,4 A Top viewLuminance @ 2,8 A

UX3 current

spreading

utilizes vias

which don’t

reach top

surface.


18 April 2012 | FN

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5

I [A]

Ie [

W]

New Chip Architecture: Eliminating Droop

Performance of new high current chip design in Dragon +

601,4 mW @ 350 mA 1966 mW @ 1,4 A 3199 mW @ 3 A


18 April 2012 | FN

Summary **

High Efficiency Pico-Projector Design is possible:

• Select the highest efficacy LED available:

• Select the appropriate optical architecture

• Provide adequate thermal management

• Drive electronics selection for cost , efficacy and

size.


18 April 2012 | FN

Thank you

Presented by

Francis Nguyen, Senior Product Marketing Manager

OSRAM Opto Semiconductors Inc.

1150 Kifer Road, Ste 100

Sunnyvale, CA 94086

Email [email protected]

Tel (408) 962-3753

mailto:[email protected]



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LEDs for Pico Projectors BA SID Chapter/PDF and Images... · Hong Kong - Headquarter Asia - Sales Asia Pacific - Marketing Asia Pacific Yokohama - Sales Japan - Marketing Japan -